The Lunkenheimer slurry valves are a particular brand of angle valve and Y-pattern valve. These slurry valves are used primarily in processing plants for the refining of Alumina, but have other applications where the flow of material, having abrasive components, is to be controlled. Such valves when used for the control of flow of material, but also, because of the nature of the material, are subject to the build-up of scale on the valve seat and the valve closure member within the valve. With this type of valve scale can be periodically removed without dismantling the valve.
Such valves may take a variety of forms, but all have a valve body defining an inlet port and an outlet port, a valve seat at the inlet or outlet port, a valve closure member moveable towards and away from the valve seat to open and close the valve during normal operation. This is achieved by relatively rotating an internally threaded yoke bush around a correspondingly externally threaded valve stem to achieve axial movement of the valve closure member to move it towards and away from the valve seat with either the valve stem rotating or the yoke bush rotating.
In order to remove scale from the opposing faces of the valve seat and the valve closure member, with the valve closure member positioned against the valve seat, the valve stem and the yoke bush are locked to each other. Therefore axial movement of the valve stem within the yoke bush and movement of the valve closure member away from the valve seat is prevented to allow the valve stem and yoke bush to rotate in unison to grind any scale away from the valve seat and the valve closure member.
The yoke bush carries a yoke bush handle to rotate the yoke bush thereby enabling opening and closing of the valve. In an alternative embodiment a gear mechanism engages with and rotates the yoke bush to open and close the valve. A torque reactor pin is provided which engages with an axially extending slot within the valve stem, or a collar surrounding the valve stem, in order to prevent rotation of the stem when the valve is operated by the yoke bush handle or gears. In some embodiments the valve is operated by its own valve stem handle, in which case the torque reactor pin engages the yoke bush to prevent the yoke bush from rotating.
A stem jam nut is threadably received around the valve stem above the yoke bush and is rotatable to move along the valve stem to a position against either the yoke bush handle, or the alternative gear mechanism which rotates the yoke bush, whereby the jam nut jams the yoke bush and the valve stem together such that they will rotate in unison when the valve stem is rotated by the yoke bush handle or alternatively by the valve stem handle carried by an upper end of the valve stem, or by gears where fitted. This in turn rotates the valve closure member relative to the valve seat to grind scale from both the valve seat and the valve closure member. In grinding, the yoke bush handle, valve stem handle or gear(s) are usually rotated continually in one direction but may alternatively be rotated back and forth. During this process it may be necessary to reposition the valve closure member by loosening the stem jam nut, moving the valve closure member and tightening the stem jam nut. This may be repeated several times as the build-up of scale is progressively ground away.
In order to jam or lock the valve stem and yoke bush together considerable force has to be used on the stem jam nut to rotate it firmly against either the yoke bush handle or the alternative gear mechanism, whichever is used, to allow rotation of the yoke bush relative to the valve stem. For this purpose a hammer, in the case of large valves a very large hammer is used. The necessity to use a hammer to tighten the jam nut leads to the possibility of injury to the worker as well as damage to the stem jam nut itself.
There has arisen a need to avoid the use of stem jam nuts that require the use of a hammer in order to lock (jam) the valve stem and the yoke bush together during the scale grinding operation.